This invention relates to plugging devices and more particularly to plugs for altering the flow of coolant in a nuclear reactor.
Conventional pressurized water reactors comprise a reactor vessel with a reactive core disposed therein which produces heat in a manner well understood in the art. A water coolant is circulated through the reactor vessel and in heat transfer relationship with the core so that heat is transferred from the core to the water coolant. The reactive core generally comprises a plurality of fuel assemblies comprising nuclear fuel. The fuel assemblies are surrounded by a plurality of vertical metal baffle plates that define the outer limits of the core. Although the baffle plates are joined together to form an outer perimeter for the core, the individual baffle plates are not welded together. Since the baffle plates are not welded together, small gaps may exist between two adjacent baffle plates. Because the baffle plates serve to direct the flow of reactor coolant water through the reactor core, the small gaps between the baffle plates do not detract from the performance of this function. However, since a substantial pressure differential may exist across the baffle plates, it is possible for small streams of high velocity reactor coolant to be established through the gaps between these baffle plates. These streams of reactor coolant can cause vibrations in the fuel assemblies or otherwise damage the fuel assemblies.
One solution to this baffle jetting of coolant is disclosed in copending application Ser. No. 252,116, filed Apr. 8, 1981 in the name of E. P. Shields entitled "Baffle Maintenance Apparatus" and assigned to the Westinghouse Electric Corporation. In the copending application there is described apparatus for reducing the size of the gaps between the baffle plates to thereby reduce the jetting of coolant therethrough.
Another solution to the problem of baffle jetting is disclosed in copending application Ser. No. 466,464, filed Feb. 15, 1983 in the name of R. W. Tolino et al. entitled "Core Barrel Plug" and assigned to the Westinghouse Electric Corporation. In the Tolino et al. copending application there is described a core barrel plug capable of being remotely installed in a port of a core barrel of a pressurized water nuclear reactor for converting the reactor from a by-pass downflow configuration to a by-pass upflow configuration and thereby reducing the pressure differential across the baffle plates to reduce the baffle jetting problem. However, the Tolino et al. core barrel plug did not provide a means to automatically prevent overexpansion of the core barrel plug.
While there exists in the art methods and apparatus for reducing or eliminating the jetting of coolant through the gaps between baffle plates, what is needed is a device to alter the pressure differential across the baffle plates to eliminate or reduce the cause of the problem while preventing overexpansion of the apparatus.